TM 5-6675-318-14
(5) The squarewave output of U11 drives the ground-based transistor pair Q9
on the positive half-cycle and Q13 on the negative half-cycle. The transistor Q17
p r o v i d e s the necessary current gain to gate the FET Q25. The transistor Q18 pro-
v i d e s i n v e r s i o n a s w e l l a s g a i n f o r t h e F E T Q 2 6 . T h e FET switching action provides
the current required to microstep the plotter motor.
P o w e r supply assembly.
The power supply consists of three PCAs, a rear panel,
aj.
and the power transformer, which is mounted in the lower case assembly.
ak.
Primary Circuits.
The ac line input connection is through the receptacle
m o u n t e d o n t h e r e a r p a n e l . T h e ac line fuse holder is also mounted here. From the
r e a r panel, the ac input is wired to the primary PCA A5. Mounted on this PCA are
the broad band line filters L1 and L2, the LINE switch S1, and the voltage selection
jumpers W1-W3. T h e s e jumpers are inserted in sockets to match the plotter primary
circuits to one of four ac line voltages.
J a c k J1 connects the primary PCA with the
p r i m a r y s i d e o f t h e p o w e r t r a n s f o r m e r T 1 . T h e secondary of the transformer is
connected through J5 to the filter and rectifier circuits of the power supply PCA
A4. This rectifier circuit supplies the plus and minus 34 volts which supplies the
m a i n power supply and the X- and Y-motors.
POWER SUPPLY OUTPUTS
Table 3-17.
Type
Use
Supply
Z e n e r regulated and balanced
34 V
M o t o r driver and power
supply circuits
Zener
regulated
5 V ref
Power supply reference,
reset, and chart hold
Zener
regulated
+12 V aux
P o w e r supply operation
Regulated
switching
supply
+5 V
Plotter operating voltage
Regulated
switching
supply
+12 V
Plotter operating voltage
Zener
regulated
+ F E T gate supply
+46 V
Zener
regulated
- F E T gate supply
-22 V
Zener
regulated
Plotter operating voltage
-12 V
Interlocked
M o t o r driver and balance
12 V
circuit shutdown
a 1 . R e f e r e n c e s u p p l y . T h e +34 volt main power is the source for the reference
supply which controls all other power supply voltages. This Zener-regulated supply
produces a +5 volt reference and a +12 volt auxiliary supply. These voltages come
up first and are used to control the switching supplies, balance circuit, and the
20 kHz oscillator circuit.
3-134
